The electric motor and reduction gearing that replace a conventional engine and transmission — genuinely simple compared with an internal combustion drivetrain, with early production rear units carrying more documented whine and bearing complaints than later, revised versions.
With no pistons, valves, or multi-speed transmission, a Tesla drive unit has dramatically fewer wear points than a conventional engine and gearbox — the main moving parts are the rotor, bearings, and a single-speed reduction gear. Early rear drive units, particularly on 2012–2015 Model S, had a documented pattern of whine noise and, in a subset of cases, bearing wear requiring replacement under warranty. Later production years saw running revisions that meaningfully improved this, and front/rear dual-motor configurations distribute wear differently than earlier single-motor layouts.
Not a guarantee, but a pattern seen consistently across owner forums and independent-garage reporting.
Whine or bearing-related symptoms, on affected early units, most commonly surfaced within this range, often addressed under warranty.
Units without early symptoms, or already replaced under warranty, commonly continue reliably well beyond this point.
Listen for a whine or grinding noise under both acceleration and regenerative braking deceleration during the test drive.
Ask whether the drive unit has ever been replaced, and if so, whether it was done under warranty with documentation.
On dual-motor vehicles, ask whether the noise (if present) comes from the front or rear unit, since this affects diagnosis and repair scope.
Model-specific pages, with notes on how it behaves in that particular car.